1. Field of the Invention
This invention relates to a vertical-type injection molding machine which can realize reduction of size and can switch materials efficiently to meet with flexible manufacturing of various types of products in small quantities without interruption of operation.
2. Description of the Related Art
The increase of frequency in making arrangements to cope with flexible manufacturing of various types of products in small quantities in recent years has a great influence on productivity. In order to reduce time for arrangements to switch materials, an improved vertical-type injection molding machine is disclosed in, for example, Japanese Patent Publication No. SHO 63-23892, in which a plurality of injection heads are supported on a turn table turnable on a fixed base about a vertical axis, and a plurality of sets of fixed and movable mold halves concentrically mounted respectively on upper and lower rotary discs via upper and lower attachment plates, the rotary discs being turnable under the fixed base about the same vertical axis.
In the known vertical-type injection molding machine, the upper mold half of upper and lower mold halves which is toward an injection nozzle is a fixed mold half and the lower mold half remote from the injection nozzle is a movable mold half. The used injection head is shifted to the material switching position when the material of one color is changed to that of another color, while another injection head for which arrangements for the following injecting operation has been previously completed is shifted to the injecting position. Thus the change of color of material is performed within a short time. Since the pluraility sets of movable and fixed mold halves can be switched one another, it is possible to form different shapes of molded products by switching necessary mold sets.
However, the vertical-type injection molding machine disclosed in the above-identified publication has a rather complicated structure. Further, partly since the fixed base is located centrally of the machine, and partly since the injection heads are located above the fixed base while the plural sets of upper and lower mold halves are located under the fixed base, the upper mold half must be fixed and the lower mold half must be movable, in order to reduce upward and downward strokes of the injection nozzle to a minimum.
Further, when a slide fastener chain having a pair of interengaged coupling element rows mounted centrally on a pair of continuous fastener tapes along its entire length is processed with high dimensional precision while it is continuously fed, it is necessary to control the tension of the chain with very high precision. Accordingly, when the vertical-type injection molding machine disclosed in the above-identified publication is used in processing a slide fastener chain, the slide fastener chain must be conveyed hanging in midair in contact with the surface of the fixed upper mold half. If the chain was guided and supported on the movable lower mold half, the conveyer for the slide fastener chain should have been raised and lowered in synchronism with the movement of the lower mold half, and the structure would have been complicated and large-sized so that the machine could not have been put into practical use.
On the other hand, in the conventional injection molding machine equipped with no cleaner, a lost shot is made into the mold during the switching of the materials. Since operations such as moving of the injection nozzle, opening and closing of the mold and clamping of the mold for every lost shot are performed according to the ordinary injection molding procedure, time needed for switching materials coincides with time needed for ordinary injection molding, thus resulting in a great time loss in continuous flexible manufacturing.
With the foregoing problems in view, it is an object of this invention to provide a vertical-type injection molding machine which utilizes the spacewise advantage of the conventional vertical-type injection molding machine in view of that there should be small economical influence on flexible manufacturing even a small time loss during the switching of materials is involved, and which is simple in mechanism and secures a high dimensional precision of products and can sharply reduce arrangements, such as color change and material switching, compared to conventional.